The Confederate battle emblem on the Mississippi flag is unconstitutional because it’s a “vestige” of slavery, an attorney argues in an update to his lawsuit seeking to change the banner.

Carlos Moore of Grenada, Mississippi, filed new arguments Thursday in a lawsuit he originally filed Monday. In the new arguments, Moore says the emblem used by some Confederate troops during the Civil War violates the 13th Amendment to the U.S. Constitution, which outlawed slavery.

Moore also expands his original argument that the flag violates the 14th Amendment’s equal protection rights of African-American residents of Mississippi, including himself. He argues in the update that the flag also violates equal protection rights for people who live outside the state.

“Mississippi is the only state that includes a symbol of a treacherous and insurrectionist Confederate army in its official state flag, restricting the liberty to be free from such tyranny said non-residents enjoy in all other states,” Moore wrote Thursday.

The lawsuit is against Republican Gov. Phil Bryant, who has said Mississippi voters should decide whether to redesign the 122-year-old banner. Bryant spokesman Clay Chandler called the lawsuit “frivolous.”

At the request of Sons of Confederate Veterans, Bryant recently proclaimed April as Confederate Heritage Month.

The public display of Confederate symbols has been widely debated since the slayings of nine black worshippers at a Charleston, South Carolina, church in June. The white suspect had previously posed for online photos with the rebel flag, which has a red field with a blue X dotted by 13 white stars.

Since the Charleston attacks, several Mississippi cities and counties and some universities have stopped flying the state flag. Moore filed his lawsuit several days after legislative leaders said they could not get consensus on bills that would either remove the Confederate symbol from the flag or withdraw state money from public entities that refuse to fly the banner.

A hearing on the flag lawsuit will be set after Democratic Attorney General Jim Hood files a response for the state. Hood said in an interview Wednesday that he thinks the flag hurts Mississippi but he will defend the lawsuit because it’s his duty as the state’s top legal officer.